The towpath has some rocks mixed in with the stone dust, but generally not too much of an issue. It's not a trail per se. You do need to keep an eye on your footing the whole time, but I wouldn't worry too much about stepping on sharp rocks. I train a lot in Nike Frees, and run on the towpath when I have to - rocks generally aren't an issue on that section.
David S. Pumpkins wrote:
Other question is if this trail has rocks and if there's the potential to feel those rocks on trail in the lighter shoes. Doubt they have a skid plate like trail racers might.
I'd be more concerned about not being used to the surface. Like the OP, I've got a history of upper hamstring tendonitis, and I can vouch that running extended distances on the towpath (more than about 10 miles) aggravates my hips and my ankles. It's flat, but the slight slipping with each push-off as you run can really snowball over time. As I mentioned, I've done some MP work on that section - it's always resulted in tender hamstrings and sore ankles (peroneal, post tib, and plantar).
If you have any issues with hip stabilty when you run, the crushed stone path may aggravate those. You personally might be fine, but there's no way to know, since you haven't trained on this surface (unless you have, and I'm missing something).
I know people with stress fracture histories who like running on the towpath for injury prevention. But I also know that people with stability/tendonitis issues (including myself) find that the towpath aggravates those issues, and try to limit our runs on it.